The present invention relates to information retrieval, and more specifically, to the efficient access of full text indexes.
There has been a rapid increase in the volume of information available on the Internet and other sources. One widely used method for users to search and access this information is known as full text search, in which a search engine examines all of the words in every stored document as it tries to match search words supplied by the user. Full text search is usually divided into two tasks: indexing and searching. The indexing stage will scan the text of all the documents and build a list of search terms, called a full text index. In the search stage, only the full text index is referenced rather than the text of the original documents.
Traditional structured databases store more and more semi-structured and unstructured textual information, which requires the full-text search to be integrated. Consequently, full-text indexes and their efficient access methods are critical in modern information retrieval. Full-text indexes have been augmented to support requirements beyond simple keyword search. More and more querying features on structured data are supported by full-text indexes directly. For example, advanced features like fielded search, numeric search, and XML support have been proposed and implemented inside full-text search.
A join is an operation that combines records from two tables in a relational database. A join can be used to combine fields from tables using values common to each. With the support of searching structured data in full-text indexes, similar join operations are also useful in full-text searches.